The hand saw business has been dominated for many years by small two stroke petrol engined saws. The advantages of such portable, self contained hand power saws for use in the street, on site, etc. are clear. Nevertheless, there has also been a steady market for fluid-powered saws, both floor and hand, for use where air or hydraulic fluid supplies are readily available. For example, if a crew required to carry out a particular task utilises pneumatic breakers for which a small compressor is required or hydraulic breakers where a hydraulic supply is required, it is more convenient to use an air or hydraulic saw and thus utilise the same power supply than to have to carry two stroke petrol for a petrol saw. Another advantage of using an air or hydraulic saw is that they are safer to use, for example when working in a trench.
Because of these desirable features, conversion units have become available for some of the known petrol hand saws. However, these saws are not designed as fluid-powered saws and have certain disadvantages. For example, due to the physical size of even a small petrol engine, the proximity of the engine air intake to the dust and grit generated by the cutting operation of the blade and the proximity to sparks created by the cutting operation, the engine is normally positioned away from the blade. The blade is therefore driven by a belt or other suitable transmission means. When such a saw is converted for use with an air or hydraulic motor, the existing transmission is utilised and thus the air or hydraulic motor is similarly positioned away from the blade instead of positioned to provide direct drive as would normally be the case for a fluid-motor driven saw. Thus, although an air or hydraulic saw is provided, it is more bulky and less manoeuvrable than a saw specifically designed to be powered by a fluid motor. Additionally, there is increased mechanical complexity and loss of power as would be typical in a petrol saw. The majority of fluid saws developed so far have been for use as floor saws which have improved in style and performance over the last few years.
In some instances, fluid saws have been designed for conversion between use as a hand saw and use as a floor saw. The main problem in converting a hand saw to a floor saw is the positioning of the fluid safety shut off valve. In the case of a hand saw, the valve is located on the handle whereas, on a floor saw, the same valve is ideally located on the steering handlebar assembly. In the case of a convertable saw, a mechanical linkage is provided to operate the valve which is located on the handle of the saw. Usually, a bowden cable connection is used, although other types of connection have been tried. However, the more efficient and reliable connections are expensive and all mechanical linkages have the severe disadvantage that, if the linkage system fails, the operator must leave the saw controls to manipulate the fluid control on the hand saw. This can be extremely dangerous.
It is an object of the present invention to provide a fluid saw which can be easily and effectly converted for use either as a hand saw or as a floor saw and which will result in reliable and safe operation in both modes.